The present invention relates to an ink amount detecting device, for use, in particular, in a stencil duplicator.
In a co-pending patent application filed for the same assignee as the present application, Ser. No. 77,547, a stencil duplicator has been proposed, which comprises a porous cylindrical drum which is supported to rotate around its central axis and is adapted to support a stencil sheet wrapped around it, an ink supply roller which is supported so as to rotate around its central axis arranged in parallel to the central axis of said drum with part of its outer peripheral surface being kept in contact with part of the inner peripheral surface of said drum, a means for supplying continuously an ink layer of a predetermined thickness onto the outer peripheral surface of said roller only when said roller rotates, and a means for exerting pressing force against the part of the outer peripheral surface of said drum which is opposite to the part of the inner peripheral surface of said drum at which said ink supply roller contacts said drum. In this connection, in the copending patent application, as the means for supplying continuously an ink layer of a predetermined thickness onto the outer peripheral surface of the ink supply roller, it has been proposed to provide an ink deposit on the outer peripheral surface of the ink supply roller and to provide a squeeze element such as a squeeze roller in close proximity to the outer peripheral surface of the ink supply roller so as substantially to prevent the ink deposit from being transferred together with the outer peripheral surface of the ink supply roller as it rotates, so that ink delivered through a thin clearance formed between the ink supply roller and the squeeze element forms the ink layer of a predetermined thickness to be provided on the outer peripheral surface of the ink supply roller.
The present invention relates, in particular, to the means for supplying continuously an ink layer of a predetermined thickness onto the outer peripheral surface of the ink supply roller in a stencil duplicator such as claimed in the aforementioned co-pending patent application, and still in particular, the present invention is concerned with detecting the amount of ink in the above-described ink deposit provided on the outer peripheral surface of the ink supply roller, for the purpose of controlling the amount of ink supplied to the ink deposit. As described in the specification of the aforementioned co-pending patent application, in order to obtain a large number of highly uniform and high quality copies by stencil duplication, it is very important that the ink supply roller is supplied with an ink layer of an accurately controlled thickness, and in order to accomplish this it is also important that the ink deposit is definitely maintained within a certain size range. In order to control the size of the ink deposit, a device which is able to detect the amount of ink or the size of the ink deposit at high accuracy and quickness is required.